This invention relates to a collapsible segment for a drive train, and more particularly to a collapsible actuator mechanism for a door opening device, such as that for a vertical garage door.
Garage door opening mechanisms, commonly known as garage door operators or garage door openers, have become increasingly popular, particulary for home installation. With their increasing popularity, however, has come attendant hazards, particularly when installed in a location where small children are present. There are many documented cases where children have been severely injured or killed by garage doors when controlled by an automatic garage door operator. Typically, a child, either playing with the operating mechanism or attempting to "beat" the door as it closes, trips and falls beneath the door and is trapped by the door in its downward progression. If the door is not provided with a reversing mechanism or if the reversing mechanism does not function properly, and if the door closes across the child's chest, the chest is compressed, pinning the child and preventing air flow. If the door closes across the child's neck, strangulation or a fractured neck occurs. If the door closes elsewhere, severe injuries, normally broken bones and internal injuries, occur. Door closing forces typically exceed 100 lbs near the fully closed position.
The emerging hazards of garage door operators have lead to many suggested safety standards for the doors, including (1) automatic rollback or reversing features which will activate when the door encounters an obstruction, (2) "panic" stop switches in addition to any normal activating switch for the door, (3) a strictly manual operating switch for the door such that the door will close or open only while the switch is held closed by the person controlling the door and (4) redundant back-up capability in case of any failure of the garage door operator.
Automatic roll-back or reversing features are normally required for all modern garage door opertors. Various types of reversing mechanisms are quite common, examples being U.S. Pat. Nos. 3,719,005; 3,764,874 and 4,159,598. While such devices are effective when operable, they in turn suffer several deficiencies. If the reversing mechanism becomes inoperable for any reason, obviously the garage door will be just as dangerous as a door without the mechanism. Since the reversing mechanisms are passive devices which do not function unless an obstruction is encountered, a user may innocently continue to use a faulty opener for months or years until an unfortunate time when an obstruction is encountered and the door does not automatically reverse. Also, such devices are typically inhibited during the last one to two inches of travel of the door so that the door is not inadvertently reversed by an uneven floor surface, build up of dirt or snow and ice, or other floor obstructions. However, since proper functioning of the inhibition mechanism is subject to variables such as wear, adjustment, installation geometry and friction, often it has been found that instead of the final two inches of closure inhibiting the reversing mechanism, actually a far greater span is inhibited. Again, particularly when small children are involved, inhibiting the reversing mechanism can lead to tragic consequences.
Other advances have recently been incorporated in garage door operators. Many such operators now being marketed include a redundant reversing mechanism which reverses the door if it does not fully close within a particular duration of time. The timing mechanism adds another level of complexity to the circuitry for the garage door operator, and adds further opportunity of age or wear to cause its inaccuracy or total nonfunctioning. Furthermore, even if the timing mechanism is operating properly, the amount of time that a door may bear upon a trapped child before reverse of the door occurs may be more than enough to cause serious injury or death.
The effectiveness of garage door reversing and inhibiting mechanisms is dependent upon proper installation and maintenance, two variables which are normally outside of the control of the manufacturer of the garage door operator. What is required is a dependable device to permit release of the downward pressure of the garage door that is not dependent upon the presence or absence of electrical power, adjustment of the garage door reversing mechanism or timing mechanism, or any other feature of the garage door operator that is subject to wear or maladjustment.